The entire North Carolina coast is divided into a series of management units that are referred to as Growing Areas. Each of these Growing Areas is individually managed to determine which portions of the area are suitable for shellfish harvest, and which need to be closed to harvest. Growing Area boundaries, along with a display of which portions of the areas are open and closed to harvest, are available here.
A variety of data are collected for each area, including:
- A shoreline survey of actual and potential pollution sources impacting the area.
- Bacteriological water quality sampling data from stations located throughout the area.
- Data summarizing the impacts of rainfall and associated stormwater runoff on Growing Area water quality.
- A summary of tides, water circulation patterns, and other physical factors that influence the movement of potential contaminants within the Growing Area.
These data are summarized and analyzed in a Sanitary Survey Report, which is then used to determine the appropriate harvest classifications.
A shoreline survey is an in-field evaluation of any potential or actual pollution sources within a Growing Area watershed to determine their potential impact on shellfish growing waters and public health. These detailed surveys are completed every three years, and involve visits to properties throughout each Growing Area watershed, where potential sources of pollution such as marinas, on-site wastewater systems, agricultural areas, wastewater treatment plants, and stormwater drainage systems are all evaluated for their potential impacts on surrounding water quality. In intervening years, these surveys are updated to reflect any major changes in pollution source impacts that may have occurred. Pollution source data collected using GPS, as well as a written summary of shoreline survey findings, are each incorporated into the Sanitary Survey, and are used to help assess which portions of the Growing Area are suitable for shellfish harvest.
To learn more about the program and staff, visit the interactive Shoreline Survey StoryMap.
More than 900 sampling stations have been established throughout the North Carolina coast in order to assess the bacteriological water quality within each shellfish Growing Area. Water samples are collected a minimum of six times per year from each of these sampling stations on a random schedule, and are analyzed for the presence of fecal coliform bacteria, which is an indicator of potential contamination from either human or animal waste. The data generated are analyzed within the Sanitary Survey to determine which stations meet the national standards for safe shellfish harvesting.
A summary of the meteorological conditions that have an effect on a growing area must be made within the sanitary survey report. Rainfall and the resultant runoff can cause fecal coliform counts to increase within shellfish growing waters. Climate and weather can affect the distribution of pollutants or can be the cause of pollutant delivery to a growing area. Prevailing winds can determine the distribution of pollutants in a growing area. Rainfall patterns and intensity can affect water quality through pollutant delivery in runoff or cause flooding which can affect the volume and duration of pollutant delivery. All of these factors must be evaluated as part of the overall sanitary survey and classification of shellfish growing areas.
An evaluation of the hydrographic factors that may affect the distribution of pollutants throughout the area must be made. Examples of hydrographic factors are tidal amplitude and type, water circulation patterns, and the amount of fresh water. These factors, along with water depths and stratification caused by density (salinity and temperature) differences, and wastewater and other waste flow rates are used to determine dilution and time of transport.
Tracer dye studies provide site-specific dilution, dispersion and time of travel information. These are required at each wastewater treatment plant that has a direct discharge into shellfishing waters to determine the proper "closed safety zone" around each outfall pipe.
For more information about the shellfish growing water shoreline surveys, contact the Shellfish Sanitation Office at 252-726-6827.
A written Sanitary Survey summarizing all of the shoreline survey, bacteriological water quality, hydrologic, and meteorological data collected for each growing area is completed at least once every three years. All of this data is analyzed within the report in order to determine the appropriate harvest classifications within each Growing Area.
Sanitary Survey Reports for all North Carolina Growing Areas can be accessed by typing “Sanitary Survey” in the search box on the Division of Marine Fisheries Digital Library webpage.
The Division of Marine Fisheries is responsible for classifying all coastal waters as to their suitability for shellfish harvesting for human consumption. Shellfish growing waters can be classified as “Approved”, “Conditionally Approved”, “Restricted”, or “Prohibited”. Approved areas are consistently open to harvest, while Prohibited areas are off limits for shellfish harvest. Conditionally Approved areas can be open to harvest under certain conditions, such as dry weather when stormwater runoff is not having an impact on surrounding water quality, and Restricted waters can be used for harvest at certain times as long as the shellfish are subjected to further cleansing before they are made available for consumption. A map of areas open and closed to harvest is available here, and a detailed classification map is accessible here.
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